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[en] In this paper, a nonlinear three-dimensional finite element (FE) model was developed and validated to study the effect of seismic damage location on the response of concrete filled tube (CFT) columns at fire after earthquakes. Three analyses were conducted consecutively in the modelling, namely, cyclic, thermal and structural. Results of the cyclic loading analysis comprising residual deformations were applied as the initial condition to the thermal-stress model, replicating the seismic performance of column. Following, a nonlinear sequentially coupled-thermal stress analysis was carried out to investigate the fire response of CFT columns after the seismic event. Three damage scenarios were contemplated, considering any possible potential damages that could be generated by the earthquake loading on CFT columns. The accuracy of proposed FE model was examined by comparing the numerical results with that of available tests on fire and cyclic loading. By means of validated model, the performance of damaged CFT columns was then investigated under fire after earthquakes. The level of damage was assumed as a high damage level, presuming that the column reached 50% of its lateral resistance while still maintaining its overall stability after the earthquake. The results were presented broadly, including the axial deformation history as well as the fire resistance time for CFT columns. To have a comprehensive insight on the influence of damage location in columns, the fire response of damaged specimens was compared with that of an intact one. (Author)
[en] In Germany, regulations for hollow spaces in slab systems require 30 minutes standard fire resistance of the load-bearing steel construction. Within a current national research project a natural fire scenario for the hollow space was developed based on realistic fire loads and ventilation conditions in the hollow space. Assuming this realistic fire scenario in the hollow space, two large scale tests on an innovative composite floor system were performed to evaluate the influence on the load bearing behaviour of the floor system. The integrated and sustainable composite floor system consists of a prestressed concrete slab, an unprotected, bisected hot rolled I-profile with composite dowels either in puzzle or clothoidal shape, and removable floor panels on the top of the I-profile. This floor system ensures the opportunity to adjust the technical building installations in accordance with the use of the building. This integrated and sustainable composite floor system was developed in several research projects. The standard fire resistance R90 for the fire scenario below the slab system has already been proven successfully. In this paper, experimental investigations regarding the heating and load bearing behaviour of the innovative composite floor system under the newly developed natural fire scenario of hollow spaces are presented. In doing so, the special test set-up to realise the fire tests for the fire scenario hollow space will be described in detail. After the fire scenario for the hollow space, the specimen was subjected to the ISO standard fire curve to establish the failure temperature of the unprotected I-profile. In addition to the temperature development and the load bearing behaviour inside the innovative floor during the heating phase, the cooling phase and the influence of a web opening on the load bearing behaviour will be discussed. (Author)
[en] This paper presents the numerical assess of the robustness of a seismic-resistant steel building with self-centering moment resisting frames against progressive collapse. The numerical analyses were carried out using a 3D model developed in ABAQUS. The 3D model considers the effect of the composite slab, where composite beams and their shear connectors were modeled with a combination of shell, beam and nonlinear connector elements. All the beam-column and beam-to-beam connections were modeled using nonlinear connector elements with appropriate failure criteria, calibrated against previous experimental results. The self-centering moment resisting frame where a sudden column loss was simulated was modelled using 3D solid elements to accurately capture its local and global nonlinear behavior. Quasi-static nonlinear analyses were carried out to identify all possible failure modes and to investigate the effect of the floor slab on the overall progressive collapse resistance. Nonlinear dynamic analyses were also carried out to predict the true dynamic response and evaluate the acceptance criteria of current building design guidelines. (Author)
[en] The slim-floor building system is attractive to constructors and architects due to the integration of steel beam in the overall height of the floor, which leads to additional floor-to-floor space, used mostly in acquiring additional storeys. The concrete slab offers natural fire protection for steel beams, while the use of novel corrugated steel sheeting reduces the concrete volume, and replaces the secondary beams (for usual spans of steel structures). Currently the slim-floor solutions are applied in non-seismic regions, and there are few studies that consider continuous or semi-continuous fixing of slim-floor beams. The present study was performed with the aim to develop reliable end-plate bolted connections for slim-floor beams, capable of being applicable to buildings located in areas with seismic hazard. It is based on numerical finite element analysis, developed in two stages. In a first stage, a finite element numerical model was calibrated based on a four point bending test of a slim-floor beam. Further, a case study was analysed for the investigation of beam-to-column joints with moment resisting connections between slim-floor beams and columns. The response was investigated considering both sagging and hogging bending moment. The results are analysed in terms of moment-rotation curve characteristics and failure mechanism. (Author)
[en] Highlights: •Machine learning models were used to estimate commercial building energy consumption. •CBECS was used to train a US-wide model with five commonly available features. •Validation of the model on city-specific building data was performed for New York City. •The gradient boosting model performs best compared to Linear, SVM, and other methods. •Availability of more building features results in more accurate models. -- Abstract: Building energy consumption makes up 40% of the total energy consumption in the United States. Given that energy consumption in buildings is influenced by aspects of urban form such as density and floor-area-ratios (FAR), understanding the distribution of energy intensities is critical for city planners. This paper presents a novel technique for estimating commercial building energy consumption from a small number of building features by training machine learning models on national data from the Commercial Buildings Energy Consumption Survey (CBECS). Our results show that gradient boosting regression models perform the best at predicting commercial building energy consumption, and can make predictions that are on average within a factor of 2 from the true energy consumption values (with an score of 0.82). We validate our models using the New York City Local Law 84 energy consumption dataset, then apply them to the city of Atlanta to create aggregate energy consumption estimates. In general, the models developed only depend on five commonly accessible building and climate features, and can therefore be applied to diverse metropolitan areas in the United States and to other countries through replication of our methodology.
[en] We discuss the preliminary calculation on the performance of closed orbit feedback system for NSLSII, its relation to the requirement on BPM, floor and girder stability, power supply stability etc
[en] A suitable methodology to find the seismic floor response spectra (FRS) at a particular location of a structural system by a direct spectra-to-spectra method is presented in this work. This methodology was developed to obtain FRS inside the ITER Tokamak Complex building and the mechanical devices located in the building, as the Fusion Reactor Machine. Based on the well-established tools developed over the last decades in random vibration theory, the methodology developed totally in the frequency domain, has three main steps: First, the generation of a free-field acceleration PSD functions compatible with the Design Response Spectra; Second, the generation of the absolute acceleration PSD function at the locations of interest within the structure; Third, the determination of the FRS. To demonstrate the feasibility of the method, the FRS obtained at a different points of the Tokamak Complex are compared with the FRS obtained by means of the classical methods, based on time-histories of absolute acceleration obtained in time-domain. The comparison reveals a great accuracy of the proposed method.
[en] We will discuss several methods for measuring the tunes in the Tevatron. These methods can be separated into three classes: active, passive and hybrid. In the active method, the beam is tickled in order to obtain a FR-equency response. In the passive method, a Schottky detector which uses a resonant stripline is used to measure the Schottky spectrum of the beam. In the hybrid method, we tickle the beam using kickers, or the Tevatron Electron Lens (TEL) in order to bring the tune signal above the noise floor of the Schottky detectors. An automatic tune fitting algorithm is also under development which allows us to measure the tune without human intervention
[en] This paper deals with the estimation of fragility functions for acceleration-sensitive components of buildings subjected to earthquake action. It considers ideally coherent pulses as well as real non-pulselike ground-motion records applied to continuous building models formed by a flexural beam and a shear beam in tandem. The study advances the idea of acceleration-based dimensionless fragility functions and describes the process of their formulation. It demonstrates that the mean period of the Fourier Spectrum, , is associated with the least dispersion in the predicted dimensionless mean demand. Likewise, peak ground acceleration, PGA-, and peak ground velocity, PGV-based length scales are found to be almost equally appropriate for obtaining efficient ‘universal’ descriptions of maximum floor accelerations. Finally, this work also shows that fragility functions formulated in terms of dimensionless -terms have a superior performance in comparison with those based on conventional non-dimensionless terms (like peak or spectral acceleration values). This improved efficiency is more evident for buildings dominated by global flexural type lateral deformation over the whole intensity range and for large peak floor acceleration levels in structures with shear-governed behaviour. The suggested dimensionless fragility functions can offer a ‘universal’ description of the fragility of acceleration-sensitive components and constitute an efficient tool for a rapid seismic assessment of building contents in structures behaving at, or close to, yielding which form the biggest share in large (regional) building stock evaluations.
[en] In the present study, overall thickness profile data for the backside corrosion of the bottom floors of the same oil storage tank were collected in 2006 and 2011. A custom-developed program was used to create virtual discrete thickness data from the overall thickness profile data. Using the created discrete thickness data, the scale parameter of Gumbel plots was examined by comparison with the data from 2006 and 2011. Using the experimental findings, a method combining extreme value analysis and Bayesian inference was proposed. With the proposed method, the actual maximum depths of corrosion were accurately predicted using the detected maximum depth of corrosion. - Highlights: • Gumbel plots with Bayesian inference was developed. • The scale parameters of Gumbel plot were analyzed. • The maximum depth of corrosion was accurately predicted.